Quality of oil of clocimum (Ocimum gratissimum Linn.) as influenced by stages of harvest and shade

Abstract

Clocimum (Ocimum gratissimum Linn.), an essential oil crop introduced in Kerala from Oammu, nearly a decade ago, is slowly replacing the other eugenol yielding sources viz., clove and cinnamon oils.. Several agro-techniques have yet to be standardised for the commercial cultivation of this crop in the State. The present studies were undertaken at the Aromatic and Medicinal Plants Research Station, Odakkali during 1988-90. Two field experiments were laid out separately one to obtain information on the optimum time of harvest for getting maximum yield of quality oil and the other to study the effect of shade on the production and quality of oil. The average removal of N, P, K, Ca, Mg, Fe, Mn and Zn from the soil by clocimum has also been worked out. The treatments in one experiment consisted of five intervals of harvest (60, 75, 90, 105 and 120 days) and four levels of shade (0, 25, 50 and 75 per cent) were tried in the second experiment. Both experiments were laid out in randomised block design. The required intensity of shade was provided by erecting 'artificial pandals. A Aplab luxmeter was used for adjusting the shade intensities. The investigations revealed that herbage yield, oil yield and oil content were maximum at 60 days harvest interval (early flowering stage) and it was on par with 75 days harvest interval. With further increase in the harvest intervals these parameters were found to decrease. Sixty days harvest interval also recorded the maximum eugenol content and it was significantly superior to all other treatments. The concentration and uptake of macro and micronutrients were also maximum at this interval. Among the shade levels tried the herbage yield was maxiomum under open condition as the plants flowered early and so two harvests could be taken under this treatment while only one harvest could be obtained for the other treatments. The oil yield, oil content, eugenol content were also maximum under open conditions. The content of almost all nutrients studied did not show any particular trend except in the case of K which showed a tendency to increase with shading. The uptake of all nutrients was maximum under full illumination which decreased with increasing shade intensity. The results thus indicated that the optimum interval of harvest is between 60 and 75 days i.e ., harvesting the crop between early and maximum flowering stages. The results also revealed that maximum yield and quality of oil in clocimum can be obtained only if there is ample light infiltration. But if only a single harvest is considered the crop under 25 per cent shade can be seen to give equally good quality oil but for a lesser number of harvest that those grown under full illumination. A high eugenol content of eighty per cent obtained for clocimum in the present study also indicates that it can definitely be used as an alternative and cheap substitute to clove and cinnamon oils.